How low would you go ?

I have (2) 600 watt HPS in 6" cooltubes with a 465 cfm blower pulling air thru for both also a window A/C in the room. I can touch the palm of my hand to the cooltube glass at any spot and keep it there for as long as i want without any discomfort. I currently have the bottom of the cooltube glass 10" from tops of canopy (bulb is 2" from glass on inside) and temps at canopy are 76-79 F. I did have them at 5-6 from the canopy and temps at 80-81 F. even though the hand test said they were okay , the girls seemed to be getting a little heat stressed but i was running my nutes a little hotter at that time . So what do you think 12" from bulb with medium nutes or 8" form bulb with medium to hot nutes. Someone told me if running HID lights real close you need to back off on nutes or if running hot nutes raise lights up. So as the title says how low would you go? opinions and comments appreciated.

You bring up a good point about a subject that very seldome gets mentioned, namely "The difference between Ambiant Heat and Radiant Heat".

Radiant Heat is that warmth you feel on your face in the morning when the Sun first comes up and everything else (the pavement and the air, etc.) is still cold. It tends to travel through space and air with little or no effect, mostly heating "solid" objects that it comes in contact with.

Ambiant Heat is the "Air Temperature" in your immediate surrounding area. After the Sun has been "out" for a while, the pavement (and most other solid objects) start to warm up. This, in turn, warms up the air by "convection" rather than radiation.

The bottom line is, plants are much better at handeling "Radiant Heat" (when the heat "only" effects the plants) than they are at handeling "Ambiant Heat" (when thier whole surrounding area is hot).

I have never experienced a need to "Cut back" on nutes because of "Close Light Proximity", but then, I've never really forced the issue. This is the first I've heard of it. Since light is the foundation for photosynthesis, I would put the lights as close as you can (within reason) and do whatever you have to do with the nutrients. Hope that helps!

T.H.Cammo said:

You bring up a good point about a subject that very seldome gets mentioned, namely "The difference between Ambiant Heat and Radiant Heat".

Radiant Heat is that warmth you feel on your face in the morning when the Sun first comes up and everything else (the pavement and the air, etc.) is still cold. It tends to travel through space and air with little or no effect, mostly heating "solid" objects that it comes in contact with.

Ambiant Heat is the "Air Temperature" in your immediate surrounding area. After the Sun has been "out" for a while, the pavement (and most other solid objects) start to warm up. This, in turn, warms up the air by "convection" rather than radiation.

The bottom line is, plants are much better at handeling "Radiant Heat" (when the heat "only" effects the plants) than they are at handeling "Ambiant Heat" (when thier whole surrounding area is hot).

I have never experienced a need to "Cut back" on nutes because of "Close Light Proximity", but then, I've never really forced the issue. This is the first I've heard of it. Since light is the foundation for photosynthesis, I would put the lights as close as you can (within reason) and do whatever you have to do with the nutrients. Hope that helps!

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What i actually read somewhere ( i think it was Mel or cervantes book) is that the stronger the light "HID" the temps are increased and at higher temps plants are nute burned more easy so i guess its not really the proximity as much as the increased heat . A point was made on another forum here about coverage if lights are to close you may lose coverage some outer plants wont get enough light. I am just trying to find that sweet spot between lumens and coverage without to much heat stress or raisng air temps at the canopy to much i have fans blowing cool air conditioned air in the space between the top of the canopy and the bottom of the glass of the cool tube but that only helps with one type of heat guess i will just have to carefully play around with the distance to find that sweet spot. Thanks for the info it made me think about something i had forgotten about different types of heat I did not know they could handle Radiant heat better than ambiant heat but it makes sense. Thanks for schooling me i will send a rep your way.